1. Field of the Invention
This invention relates to an apparatus for controlling a power window regulator for opening or closing a window of a vehicle or the like by moving the window glass and, more particularly, to an apparatus for controlling a power window regulator in which, once an automatic mode switch is turned on, energization of the motor is continued even after the "ON" operation of this switch has been cancelled, thereby enabling the window glass to be automatically moved to a limited position.
2. Description of Related Art
A type of controller for a power window regulator provided in a door of a vehicle on the driver's side has a manual mode switch and an automatic mode switch provided as a means for operating the controller. Ordinarily, this type of controller has a construction described below. A relay is provided to control the energization of the motor for moving the window glass upward or downward. When the manual mode switch is turned on, the relay is operated to form a circuit for the energization of the motor. The window glass is moved upward or downward only for the period of time that the manual mode switch is in the "ON" state, thereby enabling the window glass to be moved to the desired position. A retention circuit is provided which maintains the operating state of the relay (that is forming the motor energization circuit), once the relay is operated, by turning on the automatic mode switch. This occurs even after the automatic mode switch has been turned off. An auto-stop circuit is also provided which detects a locked-rotor current which flows through the motor during the energization of the motor based on the maintained state of the relay. When the locked-rotor current is detected, the auto-stop circuit cancels the maintenance of the operating state of the relay that is effected by the retention circuit. Consequently, once the automatic mode switch is turned on, even for a short time, the operating state of the relay is maintained by the retention circuit even after the automatic mode switch has been turned off, thereby continuing the energization of the motor. Hence, the (upward or downward) movement of the window glass. When the window glass that is moved in this way reaches a limited position (at which it completely closes or opens the window), a locked-rotor current flows through the motor. The auto-stop circuit detects this locked-rotor current and cancels the operation of the relay, thereby automatically stopping the energization of the motor in response to the window glass reaching the limited position.
However, once the locked-rotor current starts flowing through the motor, it decreases as the temperature of the motor winding increases. In some cases, the locked-rotor current becomes lower than a threshold level for detection of the locked-rotor current in the auto-stop circuit. In such an event, the operation maintained by the retention circuit is not cancelled and the energization of the motor continues uncontrollably, resulting in the risk of the motor abnormally heating as well as the risk of an increase in the rate at which the vehicle battery, serving as the power source of the power window, is consumed.